Self locking thread system



Feb. 13,l 1934. J. DE RVKIELLAND 1,946,860

Filed April 20, 1932- Patented Feb. 13, 1934 PATENT OFFICE SELF Loexme THREAD srsrEM Jakob de Rytter Kielland, Vinderen, near 0510. Norway Application April 20, 1932, Serial No. 606,498, and in Norway May Z7, 1931 The present invention relates to a thread system, which is so formed, that a selflocking action is obtained between the two threaded parts (bolt and nut) when the nut is pulled into engagement with the abutting surface.

. The characteristic feature of the present thread system lies in the use in connection with a normally threaded member (bolt or nut) of another cooperating member (nut, bolt) the thread of which is formed by combining two normal threads with diierent bottom diameter, said threads being axially displaced with regard to each other a fraction of one full pitch of the thread. The prole height of the thread of the latter part will accordingly be reduced with regard to the normal thread profile and one of the inclined side surfaces of the thread will be stepped from the bottom of the deepest thread and upwards.

When the part which is provided with a combined thread of this description is used together with a normally threaded member, the edge of the normal thread during the engagement between the threads and the abutment will be pressed axially from the deepest part of the modified thread over to the step which is formed by the 'bottom part of the shallower thread, whereby the two threaded members are automatically locked against relative movement. I

On the drawing Fig. lillustrates the development of the thread system by means of an axial section through the thread. Fig. 2 is an axial seetion on a smaller scale through a normally threaded bolt and a nut provided with the modified thread.

On Fig. 1 the curve 1 shows the cross section o! a normal thread, whereas the curve'2 shows the thread profile after one of the side surfaces of the normal thread has been machined away in accordance with the invention.

The thread proille obtained in this manner is defined by a curve which passes from point 3, which is the deepest point of the normal thread,

` over an abutment 5 tothe point 4, which forms the bottom of the axially displaced shallower thread threads, may be more or less rounded ofi in order to not a'ord too much resistance against the displacement of the thread of the other member oi the system from the bottom of the deepest to the bottom of the shallowest thread. lI'he connection co between the two thread bottoms will then be formed by a curved surface, which will be inclined somewhat towards the axis of the thread adjacent the bottom of the shallowest thread.

The dotted line 6 indicates the radially and e5 axially displaced normal thread, which forms together with the normal thread 1 the modified thread profile in accordance with the present invention.

From Fig. 2 it will be seen that the bolt 7 is 70 provided with a normal thread of the Whitworth type, whereas the nut 8 is provided with the modified thread which is indicated by the curve 3, 5,

4, 2 on Fig. 1. When the nut 8 is threaded along the bolt and abuts against the fixed surface 9, it will be displaced axially with regard to the bolt until it arrives in the position illustrated on Fig.

2, in which the exterior edge of the normal thread of bolt 7 rests in the stepped part of the modified thread of nt `8. Instead oi.' using a modified a0 thread, the cross section of which is composed of two axially displaced normal threads with difierent bottom diameter, one `may also use 3 or 4 combined normal thread systems, so as to obtain several steps in the bottom of the thread.

I claim:

1. In combination with a normal or standard thread bolt, a self-locking nut having a thread the pronle of which is formed by the superposition of two normal thread proiileshaving difierent bottom diameters and being axially displaced with regard to each other a fraction of a iull pitch of the thread whereby a stepped -suriace is obtained upon one side of the modified thread.-

2. A nut as claimed in claim 1 in which the connecting surface between the different thread bottoms of the modifled thread is formed as a continuous curved surface which is inclined with respect to the ans of the thread adjacent the shallowest thread bottom.

JAKOB Dl RYITER mLLAND. 

